The average height of some girls is 143 cm. When 3 boys, with a total height of 309 cm, are included, the average height if the children becomes 135 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
143 |
|
135 |
Total value |
143 u |
309 |
135 u + 405 |
Total height of the girls
= 1 u x 143
= 143 u
Total height of the children = 143 u + 309
143 u + 309 = 135 u + 405
143 u - 135 u = 405 - 309
8 u = 96
1 u = 96 ÷ 8 = 12
Total number of children
= 1 u + 3
= 12 + 3
= 15
Answer(s): 15